Methods and systems for diversity processing based on antenna switching are described in Ahmadreza Rofougaran, “ Method and system for diversity processing based on antenna switching,” U.S. Pat. No. 8,116,259 dated Feb. 14, 2012. Aspects of one described method include switching among a plurality of antennas in a multi-antenna wireless terminal to receive packets.
An antenna receives a number of packets before switching to another antenna, where the number of packets is pre-determined or dynamically determined. According to the described method, the received packets are diversity processed where portions of a plurality of the received packets are combined to form a single data packet. The described method is also be used to transmit packets.
Wireless devices use one or more antennas to receive radio frequency (RF) signals. However, signals received by an antenna may be affected by a transmission path taken by the signals, as well as by characteristics of the receive antenna. For example, the transmission path may comprise obstacles, such as, for example, buildings and/or trees that reflect and/or attenuate transmitted signals. In addition to obstacles in the transmission path, a receive antenna may also not be tuned to receive the frequencies for the desired channel.
Wireless communication and beam forming with passive beamformers are described in Eduardo Casas and Marcus Silva, “Wireless Communication and beam forming with passive beamformers,” U.S. Pat. No. 6,992,621. Wireless communication and beamforming is performed by depopulating one or more ports of a passive beamformer such as a Butler matrix and/or by increasing the order thereof. According to a described process, an access station includes a Butler matrix that has multiple antenna ports and multiple ports; a signal processor; and a signal selection device that is capable of coupling the signal processor to a subset of the multiple ports responsive to a signal quality determination, the signal selection device adapted to switch the signal processor from a first port to a second port of the subset of ports.
One beamforming method is digital beamforming which is also supported by the Institute of Electrical and Electronics Engineers (IEEE) 802.11n/ac standards. Multiple fixed beam (usually Omni) antennas are employed. Baseband multiple input and multiple output, and beamforming (standard and beyond, for example, implicit beamforming) techniques are used.
In digital beamforming, the receiver is tuned to coherently combine signals arriving from certain directions. Signals arriving from other directions will not coherently combine and are therefore attenuated. The scheme may be reversed to create directional beams. Thus, digital beamforming is similar to working with adaptive directional antennas.